Controlling herbicide resistant radish with herbicides in the Northern Agricultural Region (NAR) of WA with a two spray strategy

Author: | Date: 18 Feb 2014

Author

Grant Thompson, Crop Circle Consulting

Take home messages

  • Herbicide resistant wild radish can be controlled well by a range of herbicides if applied early when weeds are small.
  • A two spray strategy has proven to be very effective at controlling wild radish, particularly when the first spray is effective and is done as early as possible on small weeds.
  • Know your resistance status and your best mode of action for success.

Introduction

The threat of multiple herbicide group resistant radish and ‘stacked’ resistant radish is a great concern to growers and crop protection professionals throughout the Northern Agricultural Region (NAR) of Western Australia’s grain belt.  For many years, the widespread use of effective and low cost herbicide mixes in cereals, based mainly on group I and B chemistry, has led to an alarming level of resistance in wild radish. More expensive broadleaf herbicides have also been used at below label rates for many years.  Coupled with often poor application conditions and water volumes, this has created significantly enhanced selection pressure. In many cases these radish populations have also had significant exposure to group F and C herbicide groups in both cereal and broadleaf crops.  Surviving plants to these herbicide groups over many seasons have shared resistance genetics and have created multiple herbicide group resistance within populations and individual plants, resistant to several modes of action.

Also of significant concern to the industry is the repetitive use of two new herbicides (Precept and Velocity) that contain the relatively new active pyrasulfotole (Group H). In many cases, two applications of pyrasulfotole are being applied in cereal crops to achieve acceptable wild radish control. Given the overuse and abuse of older modes of action, the industry as a whole needs to be very conscious of using this new active carefully in order to prolong its life within our farming system.

This paper demonstrates clear options for growers based on a second year of work conducted by the Northern Agricultural Region GRDC RCSN Initiative.  In 2012, work conducted by Planfarm and AHRI showed that many two spray strategies were successful in controlling multiple herbicide group resistant radish through timely application and good water volumes with robust herbicide packages. The second year of work (2013), conducted at different locations on different populations in the NAR, also demonstrates that the best practice management of multiple herbicide group resistant radish revolves around early spraying followed by a quick and timely second spray with robust herbicide rates.

Objectives

The RCSN group clearly identified several objectives for this project:

  1. Provide a Best Practice Management Guide to growers dealing with multiple herbicide group resistant radish, supported by thorough herbicide research.
  2. Test or support the projects previous findings that not only is herbicide choice important, but timing, application volumes and weed size is also important in achieving weed control.
  3. Provide opportunities for extension of these messages with field days for growers and advisers to visually inspect the trial work.

Methodology    

Three large scale experiments were conducted in 2013.

  1. Trial 1 (HUSBANDS) was at Paul Husbands’s farm in Northampton. This site was resistance tested by Elders and Plant Science Consulting and found to have concerning levels of resistance to four herbicide groups.
  2. Trial two (BROAD) was at Ian Broad’s farm at Mingenew. This site was known to several agronomists in the region as having a very hard to kill radish population.
  3. Trial 3 (JERICHO) was at Paul Messina’s farm at South Yuna. This site was an application by timing trial on a very high density population. A large scale herbicide resistance screen was also conducted at the property.

Trial 1 and 2: The BROAD and HUSBANDS trial sites were sprayed as follows:

First spray treatments at the two leaf stage of the wheat crop – applied with a TEEJET AIXR11002 nozzle at 60L/Ha, 600KPA and 12km/hr.

  1. Nil
  2. 1500ml Bromicide 200
  3. 1000ml Jaguar
  4. 670ml Velocity + 1% Hasten
Table 1. Layout of first spray treatments applied at two leaf stage of the wheat crop.

48m buffer 6m 48m buffer 6m 48m
9m nil   Velocity   Jaguar
9m bromicide 200 @ 1.5L   nil   Velocity
9m Jaguar @1.0L   Brom 200   nil
9m Velocity @670ml   jaguar   Brom 200

plots 1-14
 
plots 15 - 28
 
plots 29 - 52

The second spray treatments were applied at five leaf stage – applied with an AGROTOP AIRMIX 110 01 nozzle at two bar at 98L/Ha at 4km/hr.  The second treatments were applied at right angles across the first spray treatments in what is known as a criss-cross trial pattern.

Table 2. Second spray treatments applied at five leaf stage of the crop, over the top of the two leaf stage treatments.

Trt

Herbicide Treatment and Adjuvant

Rate/Ha or % volume

Table 2. Second spray treatments applied at five leaf stage of the crop, over the top of the two leaf stage treatments

1

nil

0

2

Velocity  + Uptake

800ml + 0.5%

3

Flight 720 EC

720ml

4

Precept 150 + metribuzin + amsul

1500ml + 60g +1%

5

Estercide Xtra 680 + Logran + Uptake

800ml + 10g + 0.5%

6

Tigrex  + Ecopar

1000ml + 200ml

7

Precept 150 + Ecopar + Amsul

1000ml + 200ml + 1%

8

Jaguar + Agritone 570 LVE

500ml + 440ml

9

Jaguar + Estercide Xtra 680

1000ml + 800ml

10

Precept 150 + Bromicide MA + Uptake

1500ml + 1000ml + 0.5%

11

Velocity + Jaguar + Estercide Xtra 680

670ml + 500ml + 800ml + 0.5%

12

FMZ 1209 + Bromicide MA

250ml + 750ml

13

Velocity + X -Pand + Uptake

670ml + 125g + 0.5%

This layout then achieved a trial that had 52 (4 x 13) treatments of 9m x 2m area, replicated 3 times.

The water sensitive paper strips placed in the crop drill row and between the drill rows at both sites (below) demonstrate excellent application coverage onto weeds and penetration through the crop at the HUSBANDS (L) and BROAD (R) sites.

Figure 1. Application coverage at BROAD and HUSBANDS sites.

Two application maps, side by side.

The second spray treatments were applied at five leaf stage – applied with an AGROTOP AIRMIX 110 01 nozzle at two bar at 98L/Ha at 4km/hr. The second treatments were applied at right angles across the first spray treatments in what is known as a criss-cross trial pattern.

The JERICHO trial was a two time of application trial, using common and new herbicide mixtures applied at either two leaf or five leaf stage of the crop, on a high density radish site.

Table 3. Herbicide treatments applied at two or five leaf stage of the crop.
Trt Herbicide Rate Unit
Herbicide/ Adjuvant Rate Unit
Adjuvant Rate Growth Stage
1 NIL
 

 
 
 
       
2 Jaguar 750 ml/ha  
 
      Z12
3 Velocity 500 ml/ha Hasten 1 %     Z12
4 Jaguar 800 ml/ha MCPA LVE 570 440 ml/ha     Z15
5 Velocity 670 ml/ha MCPA LVE 570 440 ml/ha Hasten 1% Z15
6 Logran 10 g/ha MCPA LVE 570 440 ml/ha Hasten 1% Z15
7 Aptitude (Registration pending) 200 ml/ha MCPA Amine 500 500 ml/ha     Z15

These spray treatments were applied with an AGROTOP AIRMIX 110 01 nozzle at two bar at 98L/Ha at 4km/hr. Weeds were cotyledon to two leaf at Z12, or 4-6 leaf and up to 20cm at Z15.

Resistance Profiles of the trial site populations

HUSBANDS trail site:  Glass house resistance tests by Plant Science Consulting / Belinda Eastough (Elders):

  • 100% survival to 40g Logran (B)
  • 45% survival to 2L Simazine (C)
  • 0% survival with 1400ml Bromoxynil (C)
  • 85% survival to 200ml Brodal (F)
  • 0% survival with 500ml Velocity (H,C)
  • 60% survival to 650ml 2,4-D Ester (I)

JERICHO trial site: In field resistance screen by Landmark R and D / Robert Alderman and Grant Thompson

  • 81% survival to 30g Logran (B)
  • 43% survival to 2L Atrazine (C)
  • 57% survival to 200ml Brodal (F)  40% survival to 400ml Brodal
  • 15% survival to 800ml 2,4-D Ester (I), 12% survival to 1600ml 2,4-D Ester.
  • 62% survival to 500ml Intervix (B)
  • 8% survival with 500ml Velocity (H & C)

Observations and results

The data in Table 4 (HUSBANDS) clearly demonstrates the success of the two spray strategy when Bromicide 200, Jaguar and Velocity were used at the early two leaf timing. When no late spray was used to clean up survivors, Velocity was the most reliable early spray, as indicated by 97% and 100% weed control in the two nil late spray treatments (Trt 1&14).  At 10 days after Treatment 2 (T2) was applied, Velocity at 800ml, Tigrex + Ecopar and Precept + Ecopar gave significantly higher crop phytotoxicity results (p<0.05) than the other treatments.

When there was no early spray applied, the later five leaf stage sprays (T2) were put under a great deal of pressure. With approximately 200 radish plants/m2, there was shading of radish by other radish in many plots. If the treatment did not contain a systemic mode of action, then some of the contact only modes of action were put under more pressure. This is demonstrated by the one late spray of 800ml of Velocity at five leaf stage achieving 93% control, but an early spray at the two leaf stage on much smaller weeds achieved 100% control. This trial also shows that most treatments recommended by the RCSN group were successful in controlling this population, even with the very high levels of resistance present in the test results.

Table 4. Crop Phytotoxicity (%) 11 Days after application of Treatment 2 and efficacy (% plant death) at 11 and 105 Days after Treatment 2 at HUSBANDS.

 


 

 


 

 


 

no early T1 spray

T1 1500ml Brom 200 z12

T1 1000ml Jaguar z12

T1 670ml Velocity z12

 

No.
 
T2 Treatments
Rate/Ha or % Volume
 

crop phyto 10DAA (%)

EFFICACY 10DAA (%)

EFFICACY 64DAA %

crop phyto 10DAA (%)

EFFICACY 10DAA (%)

EFFICACY 64DAA %

crop phyto 10DAA (%)

EFFICACY 10DAA (%)

EFFICACY 64DAA %

crop phyto 10DAA (%)

EFFICACY 10DAA (%)

EFFICACY 64DAA %

Table 4

1

Nil

0

20

0

0

20

93

73

20

94

90

23

96

100

2

Velocity + Uptake

800ml + 0.5%

23

54

93

23

100

100

25

100

100

25

100

100

3

Flight 720EC

720ml

15

63

100

13

98

100

13

100

100

13

100

100

4

Precept 150 + metribuzin + amsul

1500ml + 60g

7

68

100

13

100

100

10

100

100

7

100

100

5

Estercide Xtra 680 + Logram + Uptake

800ml + 10g + 0.5%

7

17

100

7

93

100

4

98

100

7

99

100

6

Tigrex + Ecopar

1000ml + 200ml

23

69

100

22

100

100

20

100

100

23

100

100

7

Precept 150 + Ecioar + Amsul

1000ml + 200ml + 1%

18

66

98

18

100

100

22

100

100

20

100

100

8

Jaguar + Agritone 570 LVE

500ml + 440ml

8

31

91

8

97

100

7

100

100

8

100

93

9

Jaguar + Estercide Xtra 680

1000ml + 800ml

10

52

100

10

99

100

10

97

100

8

100

100

10

Precept 150 + Bromicide MA + Uptake

1500ml + 1000ml + 0.5%

7

82

100

10

99

100

10

100

100

8

100

100

11

Velocity + Jaguar + Estercide Xtra 680

670ml + 500ml + 800ml + 0.5%

13

90

100

13

100

100

12

100

100

12

100

100

12

FMZ 1209 + Bromicide MA

250ml + 750ml

12

28

77

15

98

100

12

100

100

12

100

100

13

Velocity + X-Pand + Uptake

670ml + 125g + 0.5%

15

60

100

15

100

100

15

100

100

15

100

100

14

nil

0

0

0

0

0

88

67

0

81

75

1

99

97


 

 

LSD 0.01

27

62

166

28

7

172

27

7

174

22

2

7


 

 

LSD 0.05

20

46

123

20

5

127

20

5

129

16

1

5


 

 

CV

94

56

88

91

3

79

92

3

79

74

1

3

Another point of interest is that a second flush of radish occurred after a mid-season rain in July. This germination died as a result of another short dry spell and a significant amount of competition from a crop that had reached Z39 and was using all available soil moisture.

The crop effects of Flight EC (Trt 3) and Precept + metribuzin (Trt 4) were still clearly evident at 32 days after application (DAA). Radish in the Estercide + Logran treatment trial sites took a very long time to die, with many plants showing some level of twisting and distortion but no plant death at 32DAA. 

By 32DAA, the leaf burning caused by the Precept + Ecopar and Tigrex + Ecopar treatments was less evident. These burnt older leaves had almost completely senesced.   The Jaguar + MCPA treatment had many survivors growing through the herbicide effects, with survivors exhibiting the typical dark green sheen associated with group F tolerance in radish. The more robust treatment of the higher rate of Jaguar + 24D ester had very few surviving plants at this time.

 The Precept + Bromicide MA treatment was very clean at 32 DAA and there were no surviving plants or skeletons of old plants. There were also no crop symptoms visible. The Velocity + Jaguar + Estercide treatment was also extremely clean, but the treatment did noticeably thin out the crop canopy; plants were less leafy and there were less tillers per plant. 

The FMZ 1209 treatment did have some survivors when used as a stand-alone single late spray option. This is a new and experimental product, and has perhaps been used at a rate too low in this situation. The addition of 125g X-Pand to Velocity, did not affect efficacy by 10DAA, and achieved 100% control by 64DAA.

Table 5 shows that a yield advantage of 4-500kg/ha was consistently achieved if an early two leaf spray (T1) of either Bromicide 200, Jaguar or Velocity is followed up with any number of the five leaf stage spray (T2) options. Yields ranged from 2.63 - 3.06t/ha when only one late spray was applied. When the two spray strategy was implemented, yields ranged from 3.1-3.64t/ha throughout the trial. In one case, the combination of an early Bromicide 200 spray at T1 took the yield of treatment 12 (FMZ + Brom MA at five leaf stage) from 2.63t/ha to 3.64t/ha, a yield increase of 1.01t/ha. Given a radish density of 200 plants/m2, these results demonstrate the importance of spraying early for improved efficacy and yield benefits.

The return on investment from these early spray treatments is substantial. Including application costs, these early two leaf spray treatments cost, $19 - $29 per hectare.  Their application results in an increase in net profit of approximately $90-$130/ha given the consistent yield improvements of between 4-500kg/ha of wheat ($290/t).  In the case of Treatment 12, an increase of $260/ha grain returns was achieved by using 1.5L Bromicide 200 at T1 as well as the later T2 spray.

Note about table 5: numbers in bold are significantly different (P<0.05) from Trt 1.

Table 5. Crop yield (t/ha) and yield (%) compared to nil of all treatments at the HUSBANDS site.



No early T1 spray

T1 1500ml Brom 200 z12

T1 1000ml Jaguar z12

T1 670ml Velocity z12

No. T2 Treatments Rate/Ha or % Volume

Yield %

Yield t/ha

Yield %

Yield t/ha

Yield %

Yield t/ha

Yield %

Yield t/ha

1

1. Nil

0

100

2.88

100

3.12

100

3.27

100

3.17

2

2.Velocity + Uptake

800ml + 0.5%

96

2.76

103

3.20

101

3.31

104

3.25

3

3. Flight 720EC

720ml

95

2.73

103

3.22

103

3.37

104

3.29

4

Precept 150 + metribuzin + amsul

1500ml + 60g

97

2.80

101

3.17

106

3.47

101

3.19

5

Estercide Xtra 680 + Logram + Uptake

800ml + 10g + 0.5%

91

2.63

98

3.05

103

3.37

102

3.24

6

Tigrex + Ecopar

1000ml + 200ml

94

2.71

107

3.34

100

3.26

104

3.31

7

Precept 150 + Ecioar + Amsul

1000ml + 200ml + 1%

93

2.69

109

3.41

97

3.16

105

3.33

8

Jaguar + Agritone 570 LVE

500ml + 440ml

91

2.62

105

3.29

108

3.53

98

3.11

9

Jaguar + Estercide Xtra 680

1000ml + 800ml

98

2.81

112

3.5

102

3.35

105

3.32

10

Precept 150 + Bromicide MA + Uptake

1500ml + 1000ml + 0.5%

95

2.73

111

3.48

101

3.32

108

3.43

11

Velocity + Jaguar + Estercide Xtra 680

670ml + 500ml + 800ml + 0.5%

95

2.74

110

3.43

104

3.39

101

3.19

12

FMZ 1209 + Bromicide MA

250ml + 750ml

91

2.63

117

3.64

99

3.23

101

3.21

13

Velocity + X-Pand + Uptake

670ml + 125g + 0.5%

106

3.06

105

3.29

107

3.50

105

3.33

14

nil

0

66

1.91

99

3.10

98

3.21

110

3.47



 

LSD 0.01

21

0.6

11

0.33

6

0.21

9

0.30



LSD 0.05

15

0.44

8

0.25

5

0.15

7

0.22



CV

3.39

9.76

1.42

4.44

0.84

2.80

1.26

3.98

The data in Table 6 (BROADS) demonstrates the clear advantage of spraying first with either Jaguar or Velocity at the two leaf stage of the wheat crop when weeds are small. All treatments achieved 100% weed control when sprayed with the early two leaf spray of either Jaguar or Velocity. The Bromicide 200 early spray treatment also showed clear benefits in final weed control, but was not quite as reliable as the Jaguar and Velocity early treatments, with 3 of the later treatments having some survivors. With no early spray, many of the T2 (five leaf stage) treatments had surviving plants at 105 DAA.  Conditions at the time of application were not ideal, as the region was suffering from an extended heat and moisture stress period for 6 weeks. This site also had a pre-emergent application of Diuron applied by the host farmer, which did contribute to some crop phytotoxicity and radish control, as indicated by the crop phytotoxicity and weed control in the nil plots (see note following about table 5). The radish density and uniformity at this site was uneven, which also contributed to the variable control achieved in the no early spray treatments.

Note about table 6: NIL plot results relate to previous text description; numbers in bold are significantly different (P<0.05) from Trt 1.

Table 6: Crop Phytotoxicity (%) 11 Days after Application of Treatment 2 and Efficacy (% plant death) at 11 and 105 Days after Treatment 2 at BROADS.



no early T1 spray

T1 1500ml Brom 200 z12

T1 1000ml Jaguar z12

T1 670ml Velocity z12

No. T2 Treatments Rate/Ha or % Volume

crop phyto 10DAA (%)

EFFICACY 10DAA (%)

EFFICACY 64DAA %

crop phyto 10DAA (%)

EFFICACY 10DAA (%)

EFFICACY 64DAA %

crop phyto 10DAA (%)

EFFICACY 10DAA (%)

EFFICACY64 DAA %

crop phyto 10DAA (%)

EFFICACY 10DAA (%)

EFFICACY 64DAA %

1

Nil

0

23

63

96
(see  previous text)

20

100

100

20

100

100

22

100

100

2

Velocity + Uptake

800ml + 0.5%

27

43

77

28

100

100

27

100

100

27

100

100

3

Flight 720EC

720ml

17

30

80

13

98

100

13

100

100

10

100

100

4

Precept 150 + metribuzin + amsul

1500ml + 60g

12

42

97

17

100

100

18

97

100

15

100

100

5

Estercide Xtra 680 + Logram + Uptake

800ml + 10g + 0.5%

15

23

90

10

98

100

12

88

100

15

100

100

6

Tigrex + Ecopar

1000ml + 200ml

23

77

97

22

93

100

20

100

100

22

100

100

7

Precept 150 + Ecioar + Amsul

1000ml + 200ml + 1%

23

67

97

23

98

100

13

100

100

18

100

100

8

Jaguar + Agritone 570 LVE

500ml + 440ml

13

37

93

8

83

100

10

97

100

15

100

100

9

Jaguar + Estercide Xtra 680

1000ml + 800ml

17

47

93

15

80

77

8

93

100

17

100

100

10

Precept 150 + Bromicide MA + Uptake

1500ml + 1000ml + 0.5%

10

38

90

15

93

100

10

100

100

13

100

100

11

Velocity + Jaguar + Estercide Xtra 680

670ml + 500ml + 800ml + 0.5%

15

35

87

17

100

97

17

100

100

18

100

100

12

FMZ 1209 + Bromicide MA

250ml + 750ml

20

57

87

10

77

87

17

100

100

17

100

100

13

Velocity + X-Pand + Uptake

670ml + 125g + 0.5%

20

67

93

17

100

100

18

97

100

20

100

100



 

LSD 0.01

22

57

37

20

34

29

22

12

0

24

0

0



 

LSD 0.05

16

42

27

15

25

21

16

9

0

18

0

0



 

CV

52

52

18

53

16

13

63

5

0

60

0

0

Figure 2. Radish at 2nd spray timing at HUSBANDS.

Wild radish growing in the ground, pen alongside for size reference. Wild radish spread is approximately as wide as the pen.

Figure 3. Radish at 1st spray timing at JERICHO.

Wild radish growing between crop rows.

Figure 4. Crop phytotoxicity from Ecopar (Treatments 6 and 7).

Crop leaves with yellowed tips

Figure 5. Growers and advisers visit HUSBANDS site.

More than a dozen people standing in a paddock listening to a speaker.

Table 7 (JERICHO) shows that there is a significant yield improvement of between 22-36% by spraying radish at this trial site. More importantly, there is an improvement in efficacy when wild radish is sprayed early before shading occurs. Even when MCPA (grp I), a systemic herbicide, is added to Jaguar at the later five leaf spray timing, radish control declined compared to the early Jaguar spray at two leaf stage.  Velocity achieved the highest level of control (100%) at two leaf stage, but when MCPA was added and sprayed at five leaf stage, the treatment still achieved 100% control and did not suffer a reduction in efficacy like the Jaguar + MCPA treatment. The Velocity based treatments (Trt 3 and 5) were also 10-13% higher yielding than the Jaguar based treatments (Trt 2 and 4).  The data clearly shows that herbicide choice and time of application are both important factors in achieving the best weed kill and highest grain yield.

The data also clearly shows that knowledge of the herbicide resistance status is important. Treatment 6 (Group I and B) and Treatment 7 (Groups I, C, G) clearly underperformed, which is not unexpected given the in-field resistance screen results mentioned earlier.

Note about table 7: Radish pod contamination of the nil sample was significant. Yield of wheat grain had to be estimated based on proportion of radish pod to wheat grain; numbers in bold are significantly different (P<0.05) from Trt 1.

Table 7. Efficacy 76DAA (%) and crop yield (t/ha) of treatments at two different times of application at the JERICHO site.
Trt Treatments

Efficacy 76DAA %

Yield as % of untreated

Yield kg/ha

1 Nil

0

100%

1400

2 Jaguar 750 ml/ha

Z12

96

126%

1768

3 Velocity + Hasten 500ml/ha     1%

Z12

100

136%

1911

4 Jaguar + MCPA LVE 570 800ml/ha     440ml/ha

Z15

67

123%

1722

5 Velocity + MCPA LVE 570 + Hasten 670ml/ha     440ml/ha     Hasten 1%

Z15

100

136%

1905

6 Logran + MCPA LVE 570 + Hasten 10g/ha          440ml/ha     Hasten 1%

Z15

43

122%

1701

7 Aptitude* + MCPA Amine 500 200ml/ha     500ml/ha

Z15

48

127%

1774



 

 

LSD 0.01

120

20.00

280.42



 

 

LSD 0.05

85

14.00

200.01



 

 

CV

74

0.00

6.46

Discussion

The trial work conducted here fully supports the findings from the 1st year of the project (2012), that early spraying of small weeds followed by a timely second follow up spray, with a robust herbicide rate, is highly effective at controlling resistant radish populations. The 2013 data clearly shows that there are other options for the two spray strategy than the two consecutive doses of pyrasulfotole (group H). However, the data does show that herbicide mixes containing pyrasulfotole are highly effective and reliable in many conditions. The trial also shows that there are significant improvements in efficacy and grain yield by implementing a two spray strategy when radish density is high. This season had a significant dry spell for most of June, which may have emphasized the grain yield losses from late weed control. Yield gains of up to 1t/ha were achieved at the HUSBANDS site from doing the two spray strategy instead of only one.

The focus of the RCSN group was to develop alternative control options to prevent the overuse and abuse of the group H active pyrasulfotole. This trial data does show that there are several reliable alternatives to the two group H products. However, in identifying alternative options, we encounter a new problem. Many of the alternative non- group H options identified at the HUSBANDS and BROAD sites contained Bromoxynil. In our attempts to preserve and use group H wisely, we must also ensure we do not inadvertently abuse and overuse group C chemistry, specifically Bromoxynil.

The addition of 200ml Ecopar (Pyraflufen-ethyl – Grp G) to Tigrex and Precept (Trts 6 & 7) achieved consistently high radish control. Although resulting in high levels of crop phytotoxicity early, these treatments had recovered by 32DAA. However, the top two wheat leaves at the time of application had completely senesced and although there was not a significant yield loss in this dry season, yield losses could occur in a better season where more crop biomass leads to greater grain yields. If growers and advisers are willing to accept this crop effect then these treatments can also become a very handy alternative.

The data from the HUSBANDS trial also presents a few questions rather than just providing answers. The resistance testing from this site identified a poor level of activity from group B, F and I, yet the Treatment 5 (Estercide and Logran (I & B)) eventually achieved 100% control of radish when used as a stand-alone or after an early spray. It was noted that this treatment took a very long time to achieve a complete kill of wild radish, however this does cast some doubt over the value of herbicide resistance testing as a sole determinant of a population’s resistance status in a whole paddock. Actual in-paddock herbicide mode of action and rate response screens are a much more reliable method of determining a resistance status of a population.

Acknowledgements

Andrew Sandison, Peter Newman, Cameron Weeks -  Planfarm , Agrarian Management & RCSN Geraldton, Belinda Eastough – Elders, Simon Teakle – Full Flag Agronomics, Bernie Quade, Darren Chitty and Robert Alderman – Landmark, William Campbell – Nufarm, Rick Horbury – Bayer, Dave Nicholson and Steve Cosh – DAFWA Geraldton Research Support Unit, Host Farmers – Paul Husbands, Ian Broad and Paul Messina.

Contact details

Grant Thompson,

Crop Circle Consulting, PO Box 501, Geraldton, WA, 6531.

0427 652 521

grant@cropcircleconsulting.com.au